In this paper, we first analyzed the nano-magnetic fluid composition and properties. Then we studied the characteristics of nano-magnetic fluid magnetization and magnetization mechanism. In addition, we also studied the nano-Fe3O4 magnetic particle size and surface modification effect on the magnetic properties of magnetic fluids. Nano-magnetic fluid is a new type of liquid nano-composite functional material. It also has magnetism and mobility, and therefore it has many unique properties and a wide range of applications. Nano-magnetic fluid magnetization characteristic is one of its main properties, its performance and application of magnetic fluid play a decisive role.